THESIS
2020
1 online resource (xiv, 169 pages) : illustrations (some color), 1 map
Abstract
As the major seafood supplier in Asia, Hong Kong faces the challenges of water and food
security. In particular, the excessive growth of phytoplankton can cause rapid oxygen
depletion, discoloration in water, shellfish poisoning and massive fish kills. Therefore,
water quality monitoring and forecasting is important. Water transparency is a significant
parameter in water quality monitoring and forecasting model. Secchi depth and
light extinction coefficient are two major parameters of water transparency.
The light attenuation in coastal water is caused by absorption and scattering of particles
including phytoplankton, suspended material, organic matters and water itself. The
relationships between the light extinction and related water quality parameters have
been studied in various wate...[
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As the major seafood supplier in Asia, Hong Kong faces the challenges of water and food
security. In particular, the excessive growth of phytoplankton can cause rapid oxygen
depletion, discoloration in water, shellfish poisoning and massive fish kills. Therefore,
water quality monitoring and forecasting is important. Water transparency is a significant
parameter in water quality monitoring and forecasting model. Secchi depth and
light extinction coefficient are two major parameters of water transparency.
The light attenuation in coastal water is caused by absorption and scattering of particles
including phytoplankton, suspended material, organic matters and water itself. The
relationships between the light extinction and related water quality parameters have
been studied in various water regions. However, there is little systematic investigation on
light extinction in Hong Kong coastal waters. The long-term water quality data (1986-2017) has been used to study the spatial and temporal variability of light extinction
characteristics at various coastal locations in Hong Kong. It is found that in Tolo
Harbour light extinction is mainly affected by Chlorophyll-a (Chl-a), while in Victoria
Harbour suspended solids (TSS) is more important. The major infrastructure projects
(e.g. Harbour Area Treatment Scheme) have obvious effects on water transparency. A
multiple linear regression model to predict Secchi depth as a function of Chl-a, TSS and
non-algal BOD
5 is developed. An artificial neural network model is also developed for
two stations in Tolo Harbour and Victoria Harbour.
Based on the contrast theory and image analysis, a remotely controlled system for field
measurement of light extinction is developed and installed at Yim Tin Tsai Fish Culture
Zone, Tolo Harbour. It collects light intensity data and digital photos, which can be
instantly accessed in the HKUST lab. The result shows that the remotely controlled
system is applicable to predict light extinction of water on a daily basis.
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